KEVOS® MAKEOS · Manufacturing
Turning Feed for Surface Finish (Ra)
What surface finish does this feed and nose radius give, or what feed achieves the target Ra?
Theoretical arithmetic-mean roughness Ra and peak-to-valley Rt in turning from feed and tool nose radius, or the feed for a target Ra.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Calculate | choice | Find Ra from a feed, or the feed for an Ra. |
| Tool nose radius | mm | Insert nose radius. |
| Feed per revolution | mm/rev | Feed per revolution (Ra mode). |
| Target Ra | µm | Required arithmetic mean roughness from the drawing (feed mode). |
Method and formulas
- Ra ≈ 0.031553 f² ÷ R; Rt ≈ f² ÷ 8R (= 0.125 f² ÷ R).
- Feed for a target Ra: f = √(Ra × R ÷ 0.031553), with Ra and R in the same length unit.
- Example (handbook case): Ra 1 µm with a 1 mm nose radius needs a feed of 0.17802 mm/rev.
Limitations
- Theoretical geometric finish; built-up edge, vibration, tool wear and material effects make the real Ra higher.
- Wiper inserts give better finish than this relation predicts.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a finishing feed for a drawing Ra
- Trade feed against finish and cycle time
- Explain finish problems
Who it is for
- Machinists
- CNC programmers
- Manufacturing engineers
What you get
- Theoretical Ra
- Theoretical Rt (peak to valley)
- Feed
Interpreting the result
- Start from the theoretical feed and reduce it if measured finish is too rough.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1125–1131. Topic reference; no source tables or recommended settings are reproduced.
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